Five Wisconsinan tills crop out in the Cuyahoga Valley National Recreation Area in southern Cuyahoga and northern Summit Counties. Middle Wisconsinan Mogadore Till is restricted to isolated outcrops in deep valleys whereas Middle Wisconsinan Northampton till crops out throughout the area. Kent Till overlies Northampton till in the northeastern corner of the area. Late Wisconsinan Lavery and Hiram Tills are less extensive and restricted to the uplands.
The Ohio Flora Project, under the direction of the Ohio Flora Committee of The Ohio Academy of Science, was actuated in 1950. The goal of the project is the production of an illustrated Ohio Flora covering all vascular plants, native and naturalized, with keys for their identification and a county dot distribution map for each species. More than 300,000 specimens of Ohio vascular plants are housed in the state's several herbaria. These specimens provide the main source of data for the project. They have also provided the main data source for lists of endangered species in the Ohio flora, compiled recently by the Ohio Biological Survey and the Natural Heritage Program of the Ohio Department of Natural Resources.
More than one million specimens of vascular and nonvascular plants are housed in Ohio herbaria. These collections are an invaluable scientific resource. Only 13 Ohio herbaria are listed in the Index Herbariorum. This survey identifies 37 Ohio herbaria and summarizes their holdings. Details given for these herbaria include: names and addresses of curators, hours of access, strengths of the collections, and research activities of the staff.
It was nearly 90 years after Ohio was admitted to the Union before a State Herbarium was organized in Columbus. The earliest collections of vascular plants in the state were made by Manasseh Cutler (1788), Andre Michaux (1793), Frangois Andre Michaux(1802), and Thomas Nuttall (1810, 1816). By 1810, permanent residents began recording the flora and preparing herbarium specimens. First among these was Dr. Daniel Drake of Cincinnati, who was foremost in promoting the study of botany in the Ohio Valley. During the 1830s, the golden years of plant collecting by the pioneer botanists in Ohio, Drake's efforts came to fruition in his student, Dr. John L. Riddell, who through his field work, teaching, and publications on the flora and techniques for making herbarium specimens, involved a number of individuals in the study of botany early in the decade. Many of these individuals contributed specimens to the Flora of North America project of Drs. John Torrey and Asa Gray of New York City later in the decade. At this time, institutional herbaria were formed within newly organized scientific, medical, and philosophical societies, but these early attempts at institutional herbaria failed. The private herbaria of the pioneer collectors were either donated to larger institutions outside the state, left to an institution within the state that remained small or later disappeared, retained by family members, or destroyed by fire or lost. The development of private and institutional herbaria in the state was extremely quiescent from 1850 until the 1890s, after which Professor William A. Kellerman founded the State Herbarium at The Ohio State University. From specimens contributed largely by volunteers, the herbarium expanded under Professor John H. Schaffner.